The database in an Internet domain name system (DNS) server that contains the translations between domain names and their numeric IP addresses. A zone file is made up of "resource records," which are lines of text that define the forward lookup of domains to IP, the reverse lookup of IP to domains, as well as the names of DNS and mail servers. Records for aliases and other information are also provided (see DNS records). Zone files have a .DB file extension. See Internet domain name, DNS and reverse DNS.